Adolescence is a period of neuromaturation concurrent with dramatic increases in alcohol use for many youths. Recent national epidemiology data shows that in the U.S., two percent of 12-13 years old youths reported past month heavy alcohol use, and this proportion increased to 70% by ages 21-25. Of particular concern are recent statistics that show one in five high school students had their first drink before 13 years of age. During this period of escalated alcohol use, neuromaturation continues to take place. As new synapses are formed and strengthened to accommodate learned materials, environmental perturbations, such as alcohol use, likely play a critical role in determining which circuits are used and eliminated. Heavy adolescent alcohol use, compared to controls, has been associated with differences in brain morphology, neural activation, and neuropsychological performance. Evidence suggests that for adolescents, the frontal and parietal regions may be particularly vulnerable to the neurotoxic effects of alcohol. An earlier age of alcohol use and other drug use onset has been linked to greater likelihood of having a substance use disorder (SUD) later in life, higher rates of psychiatric disorders and greater psychosocial difficulties in adulthood. However, to date, the linear influence of age of alcohol use onset on neurocognitive functioning in adolescents is still poorly understood. Further, there is a dearth of studies examining the functional connectivity of frontoparietal areas involved in adolescent alcohol use. The goal of this proposal is to understand if, and how, the age of alcohol use onset (i.e., age at which alcohol use begins and age at which weekly/regular alcohol use begins) influences neuropsychological performance and neural functional connectivity. Ultimately, the knowledge gained from this project can be used to inform public health policies, such as legal age of alcohol use, and treatment programs, such as cognitive rehabilitation, in creating initiatives that are individualized and person-centered to prevent adolescent alcohol use disorder.